The use of only age and smoking history as selection criteria in population-based CT screening trials has afforded a low yield of cancer detection at significant cost. Moreover, the routine identification of indeterminate pulmonary nodules during CT screening often requires additional workup, magnifying the cost and adding potential morbidity from related interventional diagnostic procedures. We have developed a blood test for NSCLC that may address these limitations when integrated into the early detection paradigm. Specifically, we exploited the expansive autoantibody repertoire of lung cancer patients to develop a multi-marker assay that compensates for NSCLC heterogeneity. Capture proteins were selected from cDNA tumor libraries using antibodies in patient plasma and in turn used to measure tumor-associated antibodies as markers of disease. Fluorescent microarray was adapted as a platform to accommodate a multiple marker approach. Individual markers were ranked by statistical differences between case and control samples, and Receiver Operating Characteristic (ROC) was used to statistically define an optimal combination of those markers with high discriminatory value. Classifiers for a combined marker set were then built on known case and control samples and used to predict disease in available samples. Performance results indicate excellent potential for clinical utility. Having successfully completed the biomarker discovery phase of this project, the current proposal has three primary objectives: 1) To evaluate assay performance for established lung cancer diagnosed in an expanded clinical population 2) to define a role for this assay in management of radiographically identified indeterminate pulmonary nodules independent of a screening study, and 3) to confirm results that indicate this marker set may detect cancer and predict the onset of NSCLC prior to radiographic detection in a screened population. Relevance to Public Health. A blood test for lung cancer could improve the capability and cost- effectiveness of early detection as a viable strategy for reducing mortality from this disease.